SIMI VALLEY, Calif. — Eager to tangle, Republican presidential rivals Rick Perry and Mitt Romney sparred vigorously over job creation and Social Security Wednesday night in a lively campaign debate that marked a new turn in the race to pick a 2012 challenger to President Barack Obama.

"Michael Dukakis created jobs three times faster than you did, Mitt," Perry jabbed, referring to Romney's Democratic predecessor as governor of Massachusetts.

"As a matter of fact, George Bush and his predecessors created jobs at a faster rate than you did," Romney shot back at Perry, the newcomer who has quickly become the front-runner in the race.

The debate was the first of three in as many weeks, at a time when the economy is struggling, unemployment is seemingly stuck at 9.1 percent and Obama's popularity is sinking in the polls — all events that could make the GOP nomination worth more than it appeared only a few months ago.

Perry and Romney stood next to each other on the debate stage at the Ronald Reagan Presidential Library, a symbolic setting that invoked the memory of the conservative Republican who swept to two terms as president.

For much of the evening, the debate seemed to center on the competition between the two men, largely reducing their rivals to the roles of spectators looking for a way into the action.

Former Utah Gov. Jon Huntsman sided with Perry when he turned to Romney and said, "47th just isn't going to cut it, my friend," a reference to the rank Massachusetts had among the 50 states in creating jobs during Romney's term.

But he also sought to rebut Perry's claim to be chief executive of the country's top job-producing state.

"I hate to rain on the parade of the great Lone Star State governor, but as governor of Utah, we were the No. 1 job creator during my years in service," Huntsman said.

Not surprisingly, none of the GOP contenders had anything positive to say about Obama, either his record on creating jobs or the health care law they have vowed to repeal if they win the White House.

Bachmann said she would provide the "strong, bold leader in the presidency who will lead that effort. None of us should ever think that the repeal bill will just come to our desk," she said in a pledge that drew applause from the audience.

Gingrich resisted an effort to draw him into conflict with other Republicans on stage. "I'm frankly not interested in your efforts to get Republicans fighting each other," he said, sparking an even louder round of applause. He said all Republicans should "defeat efforts by the news media" to spark an internal struggle when the real objective is to defeat Obama in 2012.

But moments later, Cain said that after trying to defeat Democratic efforts to create national health care, "I'm running against Romneycare," the legislation that passed requiring residents of Massachusetts to purchase coverage.

Social Security produced more sparks, when Perry said the program was a "Ponzi scheme" and added it was a lie to tell young workers they will ever receive the benefits they have been promised.

Romney quickly referred to Perry's book, "Fed Up," in which the Texas governor said that by any measure the program was a failure. Perry also said states should be able to opt out of the program,' Romney added.

Perry was unrepentant — "You cannot keep the status quo in place and call it anything other than a Ponzi scheme," he said.

The Texas governor also made it clear he doesn't intend to take advice from Karl Rove, the former Bush political adviser who recently said some of Perry's rhetoric has been too controversial.

"Karl has been over the top for a long time now," he said.

The event was Perry's first opportunity to share a debate stage with his rivals since he joined the race last month and shot to the top of the public opinion polls. He displaced Romney as front-runner and stepped on the momentum that Bachmann had generated with her victory in a straw poll at the Iowa State Fair earlier in the summer.

A governor for more than a decade, he seemed at ease on stage in his campaign debut and moved quickly to assert his claim to having the best record of all on stage in creating jobs.

"We created 1 million jobs in the state of Texas at the same time the United States lost 2 million," he said, adding that the issue for the nation this election season is "who on this stage can get America working. Because we know for a fact that the resident of the White House cannot."

Romney threw the first jab of the evening, saying that being a career politician is a "fine profession" but not the same as having worked in the business world, as he did.

That was a reference to Perry, who moved quickly to counter.

He said Romney had indeed done well creating jobs in the business world, but "when he moved that experience to government, he had one of the lowest job creation rates in the country. ... As a matter of fact, we created more jobs in the last three months in Texas than he created in four years in Massachusetts."

Romney didn't exactly challenge that claim, but instead said Texas has no income tax, has a right-to-work law that makes it hard for unions to organize, plentiful oil and gas reserves and a Republican legislature. Massachusetts has none of those things, and he said he had turned the state's economy around.